1. Field of the Invention
The invention concerns a machine for bending or cambering a profile such as a rod, tube, bar, wire or the like. It also concerns a bending head designed to be fitted to such a machine.
2. Description of the Related Art
Current bending machines conventionally comprise a frame on which are mounted bending means having clamping jaws and a bending form provided with supporting surfaces between which the profile passes, is clamped and is then wound, the bending means being mounted on a bending head able to pivot about an axis coaxial with the axis of the bending form. In addition, these bending machines generally include a guide strip positioned upstream from the clamping jaws and a straightening element positioned upstream from the bending form. Finally, they include means for moving the profile longitudinally relative to the frame.
The main disadvantage of these bending machines lies in the fact that they only allow profiles to be bent to one side, either to the right or to the left. In addition, the positioning assembly of the clamping jaws and the assembly for moving the guide strip produce an overall size which limits the geometry of the final parts bent.
With a view to overcoming the relative disadvantage relating to one-way bending, three main types of bending machine exist at present.
First of all, a first solution consists of providing bending machines with a numerically controlled clamp adapted so as to turn the profile about its axis with a view to changing the bending direction. However, such bending machines have a first disadvantage resulting from the fact that, when changes are made to the bending direction, movements of the profile produce so-called "whiplash" phenomena which are in particular liable to alter adversely the shape of the part produced.
A second solution consists of producing bending machines provided with means for driving the bending head in rotation which are able to turn the latter about the profile.
A third solution finally consists of producing bending machines provided with a double bending head associated with means for driving this bending head in rotation about itself. However, this solution leads to the production of relatively complex bending machines and hence to a high cost.
Moreover, in a general manner, and whatever the technique adapted from among the solutions described above, all current bending machines have two major disadvantages added to those referred to above. In point of fact, and first of all, on account of their design, they all generate an overall size which limits the geometry of the final bent parts. In practice, for example, such bending machines make it difficult to produce complex pieces having in particular consecutive 180.degree. bends forming S bends. Moreover, the cycle times of these bending machines are relatively long, leading to a low production rate.
Two other types of machine, described respectively in patents FR 2.150.503 and EP 561.025 have been developed with a view to permitting cranking in two directions.
First of all, the machine described in patent FR 2.150.503 principally comprises:
a cylindrical chuck holder associated with a tooth wheel carrying two horizontal shafts equidistant from the axis of the chuck holder, each of these shafts carrying a roller and resting in cradles secured to the frame,
a system of chains and sprockets operated by jacks, provided to cooperate with the toothed wheel so as to cause the chuck holder to pivot about the axis of one or other of the shafts housed in its cradle.
Such a machine, which effectively enables tubes to be cranked in two directions, has however several disadvantages. In point of fact, and first of all, the rate of rotation of the chuck holder is not linear since it depends on the positions in which the jacks are deployed. On account of this, the precision of the cranks becomes altered adversely and is difficult to manage. Moreover, such a machine does not enable bending operations to be carried out, namely operations where the tubes are gripped and then rolled between the rollers, but simply flexing operations. Finally, the flexing assembly (chuck holders etc) is held overlapping and resting against the frame by the system of chains and sprockets associated with the jacks. On account of this, any failure in the supply circuit to these jacks leads to a reduction in the supply pressure of the latter and may lead to the flexing assembly being detached and hence to risks of damage to the latter and especially risks of injury to the personnel using it.
As regards the machine described in patent EP 561 025, this principally comprises:
a disc rotating about its axis of revolution, provided with an axial guide groove,
a slider able to move in translation in the groove,
two rollers with a fixed inter-axial distance arranged symmetrically either side of the axis of rotation of the disc, between the slider and a part of the frame,
and a double indexing means able to lock alternately one of the rollers to the slider and the other roller to the fixed part of the frame.
According to this patent, as the disc rotates, the slider is caused to move in the groove of said disc, causing the roller secured to this slider to pivot about the fixed roller.
Such a machine also enables tubes to be cranked in two directions, but also has several disadvantages. Indeed, and first of all, its flexing head is relatively bulky (minimum overall size equal to four times the diameter of the rollers) which leads to a limitation of the complexity of shapes which can be produced. Moreover, since the inter-axial distance between the rollers has to be fixed, such a machine only allows flexing operations to be achieved and not bending operations. Finally, mechanically, such a machine is subject to problems of slipping and jamming of the slider inside the groove, which leads to the necessity of exerting high forces which can result in rapid deterioration of the mechanical parts.